Art of removing tar from gas.



F. W. STEERB. ART OE REMOVING TAR FROM GAS.

Patented'Mar. 2, 1915.

APPLICATION FILED JAN. 7, 191- 8 EPA RA TO lvwentoz Tu a l ama QR memes:

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ART OF REMOVING TAR FROIE GAS;

Application filed January 7, 1914. Serial material carried in suspension therein and of such a nature that nnnute particles thereafterward.

of may be caused to aggregate into larger particles or globules, it is more particu larly intended to be applied to the removal from the gas resulting from the destructive distillation of coal, as in the operation of retort coke ovens, or other similar gases, of the tar which, in the form of minute particles, or tar-mist, is set free or formed with the gas and carried along therewith. lhe removal of this tar is an essential step in the preparation of retort coke oven gas for cornrnercial use and the recovery of its elements of value. Various means have been em ployed for the purpose, such as scrubbing the gas in or spraying it with liquid tar, cooling it to various temperatures, by pass ing it through or showering with water, causing a mechanical impact of the tar upon surfaces as in rotary separators, etc, and many combinations of these methods, most of them involvingcostly apparatus and careful manipulation have been employed without, however, s tisfactcrily solving the problem-of comple freeing the gas from in an economical manner and without loss of constituents of value,

Heretofore the application of electricity in the shape of a brush or silent discharge as a means of removing dry, pulverulent material from gas has been described in many patents and to some extent practised.

-While it has been lHlOWIl and stated that alternating electric discharges will efiect the agglomeration pended in a relatively quiescent medium, as

' been insisted by all authorities that the practical application of an electric discharge to the removal of suspended matter from a moving streamoi gas on a commercial scale requires the employment of a direct current, notwithstanding the fact that the use of an alternating current, if feasible, would present positive Specification of Letters'Patent.

have invented certain new and liquid particles sus- Patented Mar, 2, 1915,

advantages due to the high difierence of potential required and the loss of eiliciency from rectification. l have discovered, however, the course of a long continued series of experiments on a large scale, and my invention is based on the fact, that, contrary to the opinion heretofore universally held, when a stream of gas conta' mist is passed, even with great rapidity, through an alternating electric iiel minute partles of tar are caused to co or aggregate to such an extent that they can be easily thrown out of the gas or caused to deposit by gravity to an extent not attainable by any of the methods heretofore employed In practising my invention 1 do not aim to cause tar to be deposited directly by the electrical action or within the electrical field,

though some incidental deposition take apparatus wherein zhe tar is removed by impact upon the opposing surfaces as through a grid, or through a rotary separator against the sides of which it is by centrifugal force. is much more readily arrested and held by the contacting surfaces, because of the greater size of the particles and their consequently decreased surface tension than when it is subjected to the same action in its original shape of fine mist, and a most complete cleansing of the gas is efiected.

The invention will be best understood by reference to the accompanying drawing which is a diagrainmatic indication of a form of apparatus which may be used in carrying the process into efiect.

Referring to the drawing, A, indicates a gas-way leading from a source of gas,

through which the gas' to be treated passes In either case the tar from the generator,

, points -adapted to .for the electrode though I prefer an e ectrode having a surface and discharging points "of coke as described in an application for Letters Patent filed by 'medune 10, 1914, Serial No. 804,226. Within the chamber, B, andelectrically connected to the wall thereof is a cylindrical receiving electrode, D, "fofrmed :ofmetal andhaving a-smoo'th receivin'g surface all parts of which are 'approximately equally distant from the discharging surface-of the electrode, 0. The electrode, C, is connected to one of the terminals of the secondary coil of-a step-up transformer, T, theother terminal of which 'is'connected to=the wallof the chamber, B, which is grounded. The primary-coil of'the transformer, T, 're'cei'ves current from an alternating current generator, G." The coils of thetransformer, T, are so proportioned and -a current of-such potential is delivered G, that a high difference' of potential exists between the electrodes a'nda brush discharge is-=produced from the points of the electrode,(l, the electrodes being-so spaced apart as to provide sufficient space for the passage of the volume These figures may,

of gas 'to beitreated at a proper velocity,

having regard to the production of an effective electric field with the F. em-

ployed;

In practice *with the electrodes separated three and one-half inches, I have employed a current of f'romforty thousandvolts and have pass the electrodes with a ten feet per secondwith caused the gas to linear velocity of desirable results. however,- be varied to a considerable degreewithin the scope of my invention though the topasst-with such velocity'as to carry along with it the bulk of the though some incidental in the chamber, B,'will take place.

Such tar as may b'edeposited' in the chamber, B, is drawn off from the bottom through a trgpped pipe, P, to be disposed of as desire From-"thechamb'er, B, the gas'passes by a pipe, E, to a device adapted to cause'impact ofthe coalesced particles of. tar with or upen'a rec ivingsurface. Various-mechanical arran ements which will readily occur to those skilled in the art may be used for this purpose. Inpractice I have employed a Pelouze'and Audouin separator, indicated 16a of device in which at F, in which the :gas is passed through apertures and the 'tar particles are thrown against an opposed surface. Anyotherform the -tar particles are rotary "separator the alesced bodies of tar are readily thrown out of the tar-which is entirely thousand to fifty gas is always caused tar originally 'conlarity, removing the caused to come in contact with a receiving surface may, however, be, employed. In a of the gas by centrifugal action, and in any case they readily cling to any surface with which they come in contact. In this manner a most complete separation of the tar from the gas is effected. From the separator, F, the gas passes on through pipe, H, to be collected and treated manner, while the accumulated tar isdrawn oil through pipe J. I

If desired the gas may while passing through the impact apparatus or subsequently thereto be showered or Washed with Water to 'remove constituents other than the. tar which have not been aggregated by the same manner as the tar.

Such washing, however, is not required for the deposition removed by-its impact upon theopposed surfaces and is recovered in a peculiarly pure and limpidcondition. 1 A

I am aware that the process of removing tar from :gas by'causing it to come in con tactwith a solid surface, as in a grid-like structure, tofore practised. In all such cases, however, the tar has been caused to impact upon the contacting surface while still in the form of a fine mist or fog, and for this reason it has been possible toefi'ect only an approximately complete separation upon a commercial scale-of working, even though a very extensive contacting surface is employed.

B causing an increase in the weight and ad hesiveness of the individual 'ta'r particles before bringing them in contact with the receiving surface, however, I am able 'to rap idly effect a practically complete separation with a compact and relatively inexpensive form of apparatus, and with a -compara tively small differential pressure to effect the movement-of the gas;

'What I claim as-new by Letters Patent 'is:;

1. The improvement in theart of removing-tar and similar suspended particles from gas which consists in causing an agglomeration of the particles -by mo ving the gas through an electric field'o'f alternating pogas while holding the agglomerated particles 'in suspension from and desire to secure such field and afterward separating the Pil",

or rotary separator, has been here- I relatively heavy "coin any usual or desired a ing tar and similar suspendedparticles from gas which consists in causing an agglomeration of the particles bysubjecting them to the action of a brush discharge in an electric field of-alternating polarity, moving the gas through the field at such speedthat'the particles are removed from-thefield With the ma am gas and afterward separating the particles the gas and afterward separating the parm from the gas. ticles from the gas.

3. The improvement in the art of remov- In testimony whereof, I have hereunto ing tar and similar suspended particles from subscribed my name, this 31 day of Decem- 5 gas which consists in subjecting the particles her, A. D. 1913.

to the action of a brush discharge in an elec- FRANK W. STEERE. tric field of alternating polarity, moving the Witnesses: gas through the field at such speed that the VEY L. Conwm,

particles are removed from the field with WARREN S; BLAUVELT. 

